1. Field of the Invention
The present invention relates to a cleaning device for an electrophotographic image forming apparatus, such as printer, copying machine, facsimile machine, etc. More particularly, the invention relates to a cleaning device in an image forming apparatus having an improved cleaning blade arrangement.
2. Discussion of the Background
FIG. 1 is a schematic illustration showing a prior art image forming apparatus. In the image forming apparatus, a photoconductive member 1 is charged to a substantially uniform potential to sensitize its surface by a charger 2. An optical image to the surface of the photoconductive member 1 is applied from an optical system 3 for exposure to thereby form an electrostatic latent image thereon. Unnecessary charges on an area of the photoconductive member 1 such as an area corresponding to a location between a first recording paper and a second paper, or areas corresponding to sides or ends of the recording paper, wherein an image is not formed, are removed by an eraser 4. Thereafter, the latent image is developed by toner in a developing device 5 and the developed toner image is formed on the surface of the photoconductive member 1. The recording paper is supplied from a paper feeding cassette 45 by a feeding roller 46 and the recording paper is guided by guide plates 47. Furthermore, the recording paper is first stopped by registration rollers 48 and the recording paper which is synchronized with the toner image formed on the surface of the photoconductive member 1 is transported to a transfer portion. In the transfer portion, the recording paper is charged by corona discharge of a transfer charger 6 and the toner image formed on the surface of the photoconductive member 1 is transferred onto the recording paper. The charged recording paper is discharged by corona discharge of a separation charger 7 such that the electrostatically adhered recording paper is easily separated from the surface of the photoconductive member 1. Thereafter, the recording paper is guided by a guide plate 49 and is fed to a fixing device 51 by a transport member 50. The toner image formed on the recording paper is fixed by heat and pressure of the fixing device 51 and is discharged to a discharge tray 53 by a pair of discharge rollers 52. The residual toner, which has not contributed to the image transfer in the transfer process, on the surface of the photoconductive member 1 is removed by a cleaning device 9. After the toner removal, the photoconductive member 1 is discharged by corona discharge of a discharging charger (not shown) and is irradiated by light from an erase lamp 15 in order to be initialized electrostatically for repeated use.
FIGS. 2 and 3 show the prior art cleaning device 9 in detail. In the figures, reference numeral 8 indicates a charger which is located before or upstream of the cleaning device 9 and reference numeral 11 indicates a fur brush for cleaning which is disposed downstream of the charger 8 with respect to the rotational direction of the photoconductive member 1. The fur brush 11 includes conductive fibers provided on a surface of a rotation shaft 16 and a predetermined biasing voltage is applied to the conductive fibers by a bias roller 12 which is connected to a voltage source 59. The rotation shaft 16 is pivotally supported by housings 34, 37 and gear 17 is affixed to the rotation shaft 16, as shown in FIG. 3. The bias roller 12 (which is arranged in parallel and in contact with the fur brush 11) is connected with a power source, and pivotally supported by the housing 34. A gear 18 affixed to a rotation shaft of the bias roller 12 meshes with the gear 17. The fur brush 11 rotates in a clockwise direction in FIG. 2 by a motor (not shown). In this device, the toner and the surface of the photoconductive member 1 are passed by the corona discharge of the charger 8, and the polarity and voltage of the toner, and that of the photoconductive member 1 are controlled. When the remaining toner on the photoconductive member 1 passes by a seal 10 in the entrance side, the remaining toner is removed from the surface of the photoconductive member 1 by electrostatic adsorption and mechanical friction of the fur brush 11.
However, the fur brush 11 alone is not effective in removing all of the residual toner from the surface of the photoconductive member 1. The toner remaining after the fur brush 11 is scraped by mechanical friction of a cleaning blade 23, which is arranged downstream of the fur brush 11, and the toner falls on the fur brush 11. The fur brush 11 which caught the toner contacts with a flicker bar 24, thus generating vibrations in the fur brush 11. The toner is thereby separated from the fur brush 11 by the vibrations of the fur brush 11 and adhesion of the toner to the fur brush 11 is weakened. The remaining toner on the fur brush 11 is then attracted to the bias roller 12 which has a high biasing voltage applied thereto. The toner on the bias roller 12 is mechanically scraped down onto the housing 34 by a scraper 13, and the toner in a recess of the housing 34 is discharged to a predetermined location by a rotating discharge coil 14.
With reference to FIG. 2, details of the cleaning blade will now be described. FIG. 2 shows a condition in which the cleaning blade contacts the surface of the photoconductive member when a pressure solenoid is on. The cleaning blade 23 is affixed to a blade holder 32 and the blade holder 32 is connected to a blade bracket 25. In order to press or release the cleaning blade 23, one side of the blade bracket 25 is pivotally supported by a support lever 33. In addition, a middle portion of the blade bracket 25 is connected to an end of a bias spring 27 for urging the cleaning blade 23 against the surface of the photoconductive member 1, with the other end of the bias spring 27 affixed to the body of the apparatus. The blade bracket 25 is biased by the bias spring 27 to pivot in a clockwise direction in FIG. 2 on the support lever 33. As a result, the edge of the cleaning blade 23 comes in contact with the surface of the photoconductive member 1, and another side of the blade bracket 25 comes in contact with a release lever 28. One side of the release lever 28 is supported by a plunger 30 of a solenoid 29 for applying pressure to the release lever 28 and another side of the release lever 28 is connected with an end of a release spring 31. The other end of the release spring 31 is supported by the apparatus body. The tensile force provided by the release spring 31 is stronger than that of the bias spring 27 so that the release lever 28 is moved downward and the blade bracket 25 pivots in the counterclockwise direction to release the cleaning blade 23 from the surface of the photoconductive member 1 when the solenoid 29 is off.
As shown in FIG. 3, the support lever 33 is provided on one side of the blade holder 32 and an engaging portion 35 is formed on an end of the lever 33 located outside of the housing 34. A slot cam 38, which has a meandering slot, is affixed to the rotation shaft 16 of the fur brush 11, and the engaging portion 35 of lever 33 is controlled by the slot of the slot cam 38. The cleaning blade 23 is moved back and forth (as indicated by arrow 69) via blade holder 32, lever 33 and the engaging portion 35 as the slot cam 38 rotates corresponding to the rotation of the fur brush 11. At the same time, the edge of the cleaning blade 23 scrapes the surface of the photoconductive member 1. Even if a minute projecting part exists on the surface of the photoconductive member 1, the back and forth or reciprocating movement of the cleaning blade 23 prevents damage to the cleaning blade 23 which could result if the particular portion of the cleaning blade 23 repeatedly touches the small projecting part on the surface of the photoconductive member 1. Furthermore, minute paper pieces and toner piled up in the edge portion of the cleaning blade 23 are removed by the scraping action between the cleaning blade 23 and the photoconductive member 1. Currently the major purpose of the reciprocating movement of the cleaning blade 23 is the removal of accumulated paper powder and toner, since recently organic photoconductive members (which have a smooth surface and low hardness) have been widely used.
When the cleaning blade 23 is used over a long period of time, toner and other debris accumulate in the edge portions of the cleaning blade 23 which lifts up the cleaning blade 23 in that portion (or separates the blade 23 from the photoconductive member). This condition can lead to the undesirable possibility that the contact between the photoconductive member 1 and the cleaning blade 23 is insufficient and the residual toner on the surface of the photoconductive member 1 passes by the cleaning blade 23 without being removed from the surface of the photoconductive member 1. As a result, the quality of the image deteriorates. Furthermore, to accommodate needs for a high quality image, recently small diameter toner has been used, in which the fluidity of the toner is decreased, and the above mentioned problems can become very apparent.